I've always wanted a performance car that requires racing fuel. Now that I have one I'm hating it. I am mixing five gallons of 116 octane racing fuel with nine gallons 93 octane unleaded in order to get 14 gallons of 100 octane fuel. I need to do this so my car will run without detonating. Or pinging. The price tag is a staggering $115.00 per fill up. Thank God it's not a daily driver. LOL. This car required premium fuel way back in 1969. It came from the factory with a hi-compression 4 barrel 350 which has since been rebuilt. I think they shaved the heads a little which bumped up the compression even more. It runs like dirt on 93 octane fuel and it will not run on 87 octane gas. The good news is the auto industry is working quietly with the oil industry to bring back 100 octane fuel. They are doing this in order to get more performance and gas milage out of their future cars. Apparently todays 87 octane fuel isn't all that they say it is.

 

ouch $115 a fill up gets old quick...im usually in the $50 range on my truck w 87 and i dont care much for that either

 

Seems a little excessive for a production car. Can your distributor be recurved and limited to run on pump gas? Colder spark plugs, cooler thermostat also might get you into pump gas range. $115 is way too much. Good luck

 

Also forgot to mention recalibrating the carb, if it's a factory qjet it had to pass emissions. Ethanol fuels require additional enrichment. Idle tubes, and jetting will probably need to be increased for todays fuels. Email Cliff Ruggles for recommendations.
https://cliffshighperformance.com/request-a-quote

 

AHHHH I remember the good old 60's when you could pull into the local Chevron station and fill up with thier "103 octane Custom Supreme" for 31.9 per gallon. For whatever reason it was pink in color.

 

That is all I ever used in any of my cars as long as it was available. I can remember when it was .24 9/10ths. I used to bum $2.00 from my Mom and cruise town all weekend in my '57 Bel Aire HT ..... ahh, the good old days.

 

Unless your engine is radical as hell I think some super tunning would help you avoid the race gas. Or at minimum cut it way down. It does smell good!

Ill take a shot a saving you some dineros. Its likely a combo of small problems causing the pre-ignition. The high octane is bandaiding.

First, verify you are not running lean and there aren't any vac leaks.
The wrong PCV valve can cause all kinds of trouble. An adjustable is the next improvement for me. Look into it. Many dont realize the PCV is specific to each engine and it will run like crap... at... and off idle with the wrong valve spring rate.

Optomize your ignition curve especially the mechanical (could be coming in too soon) and read the plugs while jetting up the primaries until you see deep brown. What rods do you have in the secondary? AUs are what Im running. Forget what I have on the primary. I think at least two steps rich above stock 251 specs. The carb has other trick mods too.
Make sure the AVS (secondary air valve) is optimized. This one is a bitch if you cant strap the car down to a chassis dyno. It's a lot of small tweaks. Could be a touch tight. Loosen till you get WOT bog then tighten till it just goes away.

I'm running ~11:1 in my G block with ~390 at the wheels on 91-92 ethanol free with some 104 on occasion, but not required.

The only time I get knock is when ambients are 90-95+*F under low(er) rpm heavy load, say hill climbing on the threshold of a downshift from the TH400.

 

What is your static compression ratio, and what is your cranking compression? (Pull all plugs, hold throttle open, crank 3-5 revolutions to see where needle stabilizes).

I run a true 10.6:1 in the H/O, with iron heads, 16* base timing, 35-36* all in, and it has no issues with a 50:50 blend of VP110 and Shell 93. We ran it on the dyno with 4 gallons Shell 93 and a gallon of VP110, and it ran great. I'm probably going to work on dialing my race gas dilution ratio back for street use, just not a high priority at this point.

 

The rule of thumb is that each point of compression is worth about a 4% power increase.

So a 12 to 1 motor has a 12% increase over a 9 to 1 motor, all things otherwise being equal.

Hot Rod magazine did a test on a 440 Mopar and validated this.

Have you thought about methanol injection? It would be cheaper in the long run.

 

i run leaded 110 octane with lead

Paltry $7 at the pump


worth every nickel